1. Field of the Invention
Embodiments of the invention described herein pertain to the field of expansion joints. More particularly, but not by way of limitation, one or more embodiments of the invention enable an expansion joint of unlimited expansion and rotation of a pipe coupled to embodiments of the invention while maintaining containment integrity at the joint.
2. Description of the Related Art
There are a number of requirements and/or preferences associated with expansion joints. Expansion joints allow for the movement of a pipe with respect to a device to which the pipe is coupled and are required in some environments, for example power plants for safety and robust delivery of power. There are many other environments where expansion joints are used with pipe including commercial buildings, sewers and dams for example.
Current expansion joints do not allow for unlimited travel of pipe to and from a device and do not allow for unlimited rotation of a pipe with respect to a device. In addition, translational movement of pipe orthogonal to the axis of the pipe with respect to currently available expansion joints is also limited or non-existent depending on the particular joint.
Current expansion joint devices generally involve two types of mechanisms. The two main types of mechanisms used in expansion joints are bellows or a pipe traveling inside another pipe, (or use both methods combined for example). These joints are limited in the amount of travel of the pipe along the pipe axis, rotation about the pipe axis and translation orthogonal to the pipe axis that they can accommodate.
U.S. Pat. No. 3,976,312, to Murphree is an example of a bellows type expansion joint. The joint expands or contracts along the axis of the joint by stretching or compressing the bellows portion of the joint. The bellows must be thin enough to allow for stretching and compress, yet thick enough to withstand the internal pressure within the bellows at the temperature required for the installation. It is rare in the mechanical arts to combine flexibility and strength in one device and expansion joints are an example where this consideration is taken into account. In addition, bellows type expansion joints have a limited number of cycles that they are able to endure before failing. For example a bellows type expansion joint may be rated for 3,000 cycles and fail at 9,000 cycles. Maintenance of these types of joints generally involves cutting pipe and installing a new bellows type expansion joint. Maintenance of such an apparatus is thus an expensive endeavor.
U.S. Pat. No. 3,936,080 to Bennett is an example of a pipe-in-pipe expansion joint. Sleeve 30 fits inside sleeve 34 and allows for horizontal travel of sleeve 30 in and out of sleeve 34. This design makes use of two O-rings inside grooves 42 that are incapable of handling high pressure and/or temperature due to their configuration and materials of construction. Although better O-rings allow for higher temperature and pressure, in general, tightening the O-rings that here contact the pipe, results in less rotation and axial movement in the expansion joint. Translational movement orthogonal to the axis of the pipe is not possible with this type of expansion joint as there is no where for the inner sleeve to move to.
U.S. Pat. No. 4,526,409 to Schaefer is an example of an apparatus that uses both bellows and pipe-in-pipe elements. Sleeves 32 and 37 lie within bellows 12 and the sleeve 32 for example travels in and out of sleeve 37. This patent in effect makes use of both of the design element of the previous two patents described above. In addition, the device limits the length of travel of the two sleeves by employing stop members at the ends of the sleeves that limit the maximum amount of travel permitted by the device. This device suffers from the limitations of both of the previous devices in that the bellows are limited to a number of cycles and provide only limited horizontal travel without enabling unlimited rotation and provide negligible translation movement of the pipe to which the expansion joint is coupled.
For at least the limitations described above there is a need for a penetration slider seal expansion joint apparatus and method that allows for unlimited travel to and from the apparatus, unlimited rotation about the axis of the pipe and a configurable amount of translation movement orthogonal to the axis of the pipe to which the apparatus is coupled.